This application is a 371 of PCT/FR 99/00142 filed Jan. 25, 1999.
A novel material which can be used in the field of the separation and purification of gases is disclosed. Current separation techniques, whether cryogenic distillation or adsorption on zeolites, and techniques for the purification of industrial gases by cryogenic or catalytic distillation are not always capable of being optimized, either in economic terms or in terms of purity. Many studies have furthermore shown that gases such as oxygen, hydrogen or carbon monoxide react selectively and reversibly with transition metal complexes.
Thus, cobalt(II) complexes of cyclam or of cyclene easily fix atmospheric oxygen (Machida R., Kimura E., Kodama M., Inorg. Chem., 1983, 22, 2055-2061) and result in xcexc-peroxide species in aqueous media. However, the lifetime of the oxygen-comprising complexes in solution is limited as the latter can undergo irreversible decomposition reactions (Martell A. E., Basak A. K., Raleigh. C. J., Pure Appl. Chem., 1988, 60, 1325-1329). Furthermore, these species cannot be deoxygenated simply by decreasing the dioxygen partial pressure. An improvement in the reversibility, necessary in a separation process, requires stabilization of the intermediate superoxide species. Grafting the ligand to a solid matrix should, at the same time, slow down the change from the superoxide species to the xcexc-peroxide species, restrict hydrolysis reactions and facilitate the handling of the active complex (Tsuchida E., Nishide, H. Top. Curr. Chem., 1986, 32, 63-99). The incorporation of cobalt complexes with porphyrins, phthalocyanines or cyclidenes in organic or inorganic polymers, such as silica gels, and the study of the interaction of these materials with oxygen have already formed the subject of numerous studies. Generally, the complex is synthesized in a first stage and then immobilized on the polymer via a dative bond between a nitrogen atom of a pyridine or imidazole unit and the metal (Nishide H., Suzuki T., Kawakami H., Tsuchida E., J. Phys. Chem., 1994, 98, 5084-5088; Cameron J. H., Graham S., J. Chem. Soc. Dalton Trans., 1992, 385-391; Bowman R. G., Basolo F., Burwell Jr. R. L., J. Am. Chem. Soc., 1975, 97, 5125-5129). Another approach consists in attaching, in a first step, the ligand to the polymer via a covalent bond and in subsequently metallating (Wxc3x6hrle D., Gitzel J., Krawczyk G., Tsuchida E., Ohno H., Okura I., Nishisaka T., J. Macromol. Sci. Chem., 1988, A25, 1227-1254; Barnes M. J., Drago R. S., Balkus Jr. K. J., J. Am. Chem. Soc., 1988, 110, 6780-6785). Thus, the grafting to silica gel of tetraazamacrocyclic ligands and the study of the metallation of these materials have been carried out (Gros C., Rabiet F., Denat F., Brandes S., Chollet H., Guilard R., J. Chem. Soc. Dalton Trans., 1996, 1209-1214). The sol-gel process has been studied in detail (Hench L. L., West J. K., Chem. Rev., 1990, 90, 33-72) and is of major importance in the chemistry of the materials. One of the main advantages of this process is a high homogeneity of the materials obtained, thus conferring specific properties on them. Precursors of alkoxide type are among the most widely used. Thus, the hydrolysis of tetraethoxysilane in solution in an organic solvent, for example an alcohol, results in a colloidal dispersion of particles, which particles result from the polymerization of the precursor and which dispersion is referred to as a sol. This sol changes in the direction of the formation of a gel. The drying of this gel by evaporation results in a xerogel, which can itself be converted into glass or ceramic. More recently, this technique has made possible the preparation of novel organic-inorganic hybrid materials (Corriu R. J. P., Leclercq D., Angew. Chem. Int. Ed., 1996, 35, 1420-1436; Schubert U., Hxc3xcsing N., Lorenz A., Chem. Mater., 1995, 7, 2010-2027). The precursor is then an organic compound carrying one or more endings of trialkoxysilyl [Si(OR3)] or silyl [SiH3] type. Various organic species have been used, such as aromatic compounds, acetylenic units or linear and cyclic amines (Corriu R. J. P., Leclercq D., Angew. Chem. Int. Ed., 1996, 35, 1420-1436; Khatib I. S., Parish R. V., J. Organomet. Chem., 1989, 369, 9-16; Tsuda T., Fujiwara T., J. Chem. Soc. Chem. Commun., 1992, 1659-1661). Battioni et al. have used this route to incorporate manganese and iron porphyrins in a silica gel and have tested the catalytic properties of these novel materials (Battioni P., Cardin E., Louloudi M., Schxc3x6llhorn B., Spyroulias G. A., Mansuy D., Traylor T. G., Chem. Commun., 1996, 2037-2038).
The anchoring of a complex to a polymer via a dative bond between a base and the metal exhibits the advantage of activating the complex and of stabilizing the superoxide species by hindering one of the faces of the complex. However, the bond thus formed is weak. The grafting of the ligand via a covalent bond results, for its part, in a stronger material. Generally, the methods for the incorporation of the transition metal complexes in organic or inorganic matrices have to date been unable to result in materials which are compatible with the requirements of process engineering and can thus be used in industrial processes. In particular, the characteristics of such a material must be able to be adjusted in terms of specific surface, of porosity, whether this be the radius, the shape or the size distribution of the pores, and of particle size. The Applicant Company has found that the material which is a subject-matter of the present invention makes it possible to solve the problems set out hereinabove. A subject-matter of the invention is a compound of formula (I): 
in which:
W1, W2 and W3, which are identical or different, each represent, independently of one another, a divalent radical chosen from those represented by the general formula (A):
xe2x80x94[(CT1T2)nxe2x80x94[N(R4)]pxe2x80x94(CT3T4)m]lxe2x80x94xe2x80x83xe2x80x83(A)
xe2x80x83in which:
p represents an integer equal to 0 or to 1,
l represents an integer equal to 1 or to 2,
n and m, which are identical or different, each represent, independently of one another, an integer less than or equal to 3 and greater than or equal to 1, T1, T2, T3 and T4, which are identical or different, either each represent, independently of one another, a hydrogen atom, a linear or branched alkyl radical comprising from 1 to 15 carbon atoms or a [(hetero)aryl]alkyl radical comprising from 7 to 12 carbon atoms or else CT1T2 and/or CT3T4 represent a divalent group xe2x80x94(Cxe2x95x90O)xe2x80x94,
R4 represents a hydrogen atom, a linear or branched alkyl radical comprising from 1 to 15 carbon atoms which is unsubstituted or substituted by one or more functional groups, a [(hetero)aryl]alkyl radical comprising from 7 to 12 carbon atoms or a radical represented by the general formula (B):
R5xe2x80x94Si(X1)(X2)(X3)xe2x80x83xe2x80x83(B)
xe2x80x83in which:
X1, X2 and X3, which are identical or different, each represent, independently of one another, a hydrogen atom, a halogen atom or an OR6 radical, in which R6 represents a hydrogen atom or an alkyl radical comprising from 1 to 4 carbon atoms,
R5 represents a divalent radical derived from a saturated or unsaturated aliphatic hydrocarbonaceous chain comprising from 1 to 10 carbon atoms, in which chain are optionally inserted one or more structural links chosen from the arylene group or the xe2x80x94Oxe2x80x94, xe2x80x94Sxe2x80x94, xe2x80x94Oxe2x80x94C(xe2x95x90O)xe2x80x94, xe2x80x94N(R7)xe2x80x94C(xe2x95x90O)xe2x80x94 or xe2x80x94N(R7)xe2x80x94 fragments, in which fragments R7 represents a hydrogen atom, an aliphatic hydrocarbonaceous radical comprising from 1 to 6 carbon atoms, a benzyl radical or a phenethyl radical, said chain being unsubstituted or substituted by one or more radicals chosen from halogen atoms, the hydroxyl group, alkyl radicals comprising from 1 to 4 carbon atoms or benzyl or phenethyl radicals,
R1, R2 and R3, which are identical or different, each represent, independently of one another and of R4, a hydrogen atom, a linear or branched alkyl radical comprising from 1 to 15 carbon atoms which is unsubstituted or substituted by one or more functional groups, a [(hetero)aryl]alkyl radical comprising from 7 to 12 carbon atoms or a radical represented by the general formula (B) as defined above, it being understood that at least one of these cyclic nitrogens is substituted by a radical of formula (B).
Mention may be made, as compounds of formula (I) comprising three cyclic nitrogen atoms, of, for example, the compounds derived from 1,4,7-triazacyclononane, from 1,4,7-triazacyclodecane or from 1,5,8-triazacyclododecane. Mention may be made, as compounds of formula (I) comprising four cyclic nitrogen atoms, of, for example, the compounds derived from 1,4,7,10-tetraazacyclododecane (cyclene), from 1,4,7,10-tetraazacyclotridecane, from 1,4,7,10-tetraazacyclotetradecane, from 1,4,8,11-tetraazacyclotetradecane (cyclam), from 1,4,8,12-tetraazacyclopentadecane, from 1,5,9,13-tetraazacyclohexadecane or from 1,5,10,14-tetraazacyclooctadecane. Mention may be made, as compounds of formula (I) comprising five cyclic nitrogen atoms, of, for example, the compounds derived from 1,4,7,10,13-pentazacyclopentadecane, from 1,4,7,11,15-pentaazacycloctadecane or from 1,5,9,13,17-pentaazacyclooctadecane.
Mention may be made, as compounds of formula (I) comprising six cyclic nitrogen atoms, of, for example, the compounds derived from 1,4,7,10,13,16-hexaazacyclooctadecane or from 1,5,9,13,17,20-hexaazacyclotetracosane.
The term xe2x80x9cfunctional groupxe2x80x9d denotes in particular, in the definitions of R1, R2, R3 and R4, the carboxyl (CO2H), carboxamido (CONH2), sulfo (SO3H) or dihydrophosphonato (PO3H2) groups, in the esterified form.
A particular subject-matter of the invention is,
either a compound of formula (Ia), corresponding to the formula (I) as defined above in which W1, W2 and W3, which are identical or different, represent a radical of formula (A1), corresponding to the formula (A) as defined above in which p is equal to 0 and the sum n+m is equal to 2 or to 3,
or a compound of formula (Ib), corresponding to the formula (I) in which W1 represents a divalent radical of formula (A2), corresponding to the formula (A) as defined above in which p is equal to 1 and the sum n+m is equal to 2 or to 3, and W2 and W3, which are identical or different, represent a radical of formula (A1),
or a compound of formula (Ic), corresponding to the formula (I) in which W1 and W2, which are identical or different, represent a divalent radical of formula (A2) and W3 represents a radical of formula (A1).
A more particular subject-matter of the invention is,
either the compound of formula (Ia1), corresponding to the formula (Ia) as defined above in which l is equal to 1 and either W1, W2 and W3 each represent the divalent radical xe2x80x94CH2xe2x80x94CH2xe2x80x94CH2xe2x80x94 or else any one of the three groups W1, W2 or W3 represents the divalent radical xe2x80x94CH2xe2x80x94CH2xe2x80x94CH2xe2x80x94 and each of the other two groups represents the divalent radical xe2x80x94CH2xe2x80x94CH2xe2x80x94,
or the compound of formula (Ib1), corresponding to the formula (Ib) as defined above in which l is equal to 1 and either any one of the three groups W1, W2 or W3 represents the radical xe2x80x94CH2xe2x80x94CH2xe2x80x94CH2xe2x80x94N(R4)xe2x80x94CH2xe2x80x94CH2xe2x80x94, either one of the two remaining groups represents the radical xe2x80x94CH2xe2x80x94CH2xe2x80x94 and the final group represents the radical xe2x80x94CH2xe2x80x94CH2xe2x80x94CH2xe2x80x94 or else any one of the three groups W1, W2 or W3 represents the radical xe2x80x94CH2xe2x80x94CH2xe2x80x94CH2xe2x80x94N(R4)xe2x80x94CH2xe2x80x94CH2xe2x80x94CH2xe2x80x94 and the other two groups each represent the radical xe2x80x94CH2xe2x80x94CH2xe2x80x94CH2xe2x80x94.
The compound of formula (I) can be unsubstituted or substituted; when it is substituted, it is, for example, that substituted by one or more alkyl radicals comprising from 1 to 15 carbon atoms or the benzyl, picolyl or phenethyl radicals, such as, for example, 6-dodecyl-1,4,8,11-tetraazacyclotetradecane, 3-dodecyl-1,5,9,13-tetraazacyclohexadecane, 3-dodecyl-1,5,10,14-tetraazacyclooctadecane, 5,5,7,12,12,14-hexamethyl-1,4,8,11-tetraazacyclotetradecane, 1,4,7,10,13-pentaethyl-1,4,7,10,13,16-hexaazacyclooctadecane, 1,4,7,10-tetraethyl-1,4,7,10,13-pentaazacyclopentadecane, 1-methyl-1,4,8,11-tetraazacyclotetradecane, 1-benzyl-1,4,8,11-tetraazacyclotetradecane, 1-[(2-pyridyl)methyl]-1,4,8,11-tetraazacyclotetradecane, 1-[(3-pyridyl)methyl]-1,4,8,11-tetraazacyclotetradecane or 1,4-dibenzyl-1,4,8,11-tetraazacyclotetradecane.
According to a specific aspect of the present invention, a subject-matter of the latter is the compounds of formulae (Ia), (Ib) and (Ic) as defined above in which the R1, R2, R3 and R4 radicals represent either a (B) radical or a hydrogen atom and in particular the compounds of formulae (Ia1) and (Ib1) as defined above in which the R1, R2, R3 and R4 radicals represent either a (B) radical or a hydrogen atom.
According to another specific aspect of the present invention, a subject-matter of the latter is the compound of formula (I) as defined above in which R1, R2, R3 and R4 represent either a (B) radical or a radical xe2x80x94(CH2)wxe2x80x94C(xe2x95x90O)xe2x80x94V, in which V represents one of the NH2 or OR8 radicals, in which R8 represents an alkyl radical comprising from 1 to 4 carbon atoms, and w represents an integer greater than or equal to 1 and less than or equal to 6.
The radical of formula (B) as defined above is, for example, a radical of formula (B1):
xe2x80x94[CH2xe2x80x94CH(OH)]yxe2x80x94(CH2)oxe2x80x94(Q)qxe2x80x94(CH2)rxe2x80x94(Ar)sxe2x80x94(CH2)txe2x80x94(U)uxe2x80x94(CH2)vxe2x80x94Si(X)3xe2x80x83xe2x80x83(B1)
in which:
o, r, t and v, which are identical or different, each represent, independently of one another, an integer greater than or equal to 0 and less than or equal to 6,
y, q, s and u, which are identical or different, represent, independently of one another, an integer greater than or equal to 0 and less than or equal to 1,
Q and U, which are identical or different, each represent, independently of one another, an oxygen atom, a sulfur atom or one of the xe2x80x94Oxe2x80x94COxe2x80x94, xe2x80x94COxe2x80x94Oxe2x80x94, xe2x80x94NHxe2x80x94COxe2x80x94, xe2x80x94COxe2x80x94NHxe2x80x94 or xe2x80x94NHxe2x80x94 groups,
Ar represents an arylene group and in particular a phenylene group,
X represents a hydrogen atom or one of the methoxy or ethoxy radicals,
it being understood,
that, when q is equal to 1, the sum y+o is other than 0,
that, when q is equal to 1 and when u is equal to 0, the sum r+s+t+v is other than 0,
that, when u is equal to 1, v is other than 0,
that, when u is equal to 1 and when q is equal to 0, the sum y+o+r+s+t is other than 0,
that, when s is equal to 0 and when q and u are each equal to 1, the sum r+t is other than 0, and
that the sum y+o+r+t+v is less than or equal to 12.
In a preferred alternative form of the present invention, the radical of formula (B1) as defined above is chosen from the 3-silylpropyl, (4-silylphenyl)methyl, 3-(triethoxysilyl)propyl, 3-[[3-(triethoxysilyl)propyl]oxy]-2-hydroxypropyl, [4-[[[3-(triethoxysilyl)propyl]amino]methyl]phenyl]methyl, [4-(triethoxysilyl)phenyl]propyl, 3-oxo-3-[[3-(triethoxysilyl)propyl]oxy]propyl or 2-oxo-2-[[3-(triethoxysilyl)propyl]amino]ethyl radicals.
A very particular subject-matter of the invention is the compounds with the following names:
1,4,8,11-tetrakis[3-(triethoxysilyl)propyl]-1,4,8,11-tetraazacyclotetradecane,
1,4,8,11-tetrakis[[4-(triethoxysilyl)phenyl]methyl]-1,4,8,11-tetraazacyclotetradecane,
tetra[3-(triethoxysilyl)propyl]1,4,8,11-tetraazacyclotetradecane-1,4,8,11-tetrapropanoate,
1,4,8,11-tetrakis(3-silylpropyl)-1,4,8,11-tetraazacyclotetradecane,
1,4,8,11-tetrakis[(4-silylphenyl)methyl]-1,4,8,11-tetraazacyclotetradecane,
N1,N2,N3,N4-tetrakis[3-(triethoxysilyl)propyl]-1,4,8,11-tetraazacyclotetradecane-1,4,8,11-tetraacetamide,
4,11-bis[[4-(triethoxysilyl)phenyl]methyl]-1,4,8,11-tetraazacyclotetradecane-7,14-dione.
According to another aspect of the present invention, a subject-matter of the latter is a process for the preparation of the compound of formula (I) as defined above, which comprises
a) the reaction of a compound of formula (C)
Zxe2x80x94Rxe2x80x25xe2x80x94Si(X1)(X2)(X3)xe2x80x83xe2x80x83(C)
xe2x80x83in which:
X1, X2 and X3, which are identical or different, each represent, independently of one another, a hydrogen atom, a halogen atom or an OR6 radical, in which R6 represents a hydrogen atom or an alkyl radical comprising from 1 to 4 carbon atoms,
Rxe2x80x25 represents a divalent radical derived from a saturated or unsaturated aliphatic hydrocarbonaceous chain comprising from 1 to 10 carbon atoms, in which chain are optionally inserted one or more structural links chosen from the arylene group or the xe2x80x94Oxe2x80x94, xe2x80x94Sxe2x80x94, xe2x80x94Oxe2x80x94C(xe2x95x90O)xe2x80x94, xe2x80x94N(R7)xe2x80x94C(xe2x95x90O)xe2x80x94 or xe2x80x94N(R7)xe2x80x94 fragments, in which fragments R7 represents a hydrogen atom, an aliphatic hydrocarbonaceous radical comprising from 1 to 6 carbon atoms, a benzyl radical or a phenethyl radical, said chain being unsubstituted or substituted by one or more radicals chosen from halogen atoms, the hydroxyl group, alkyl radicals comprising from 1 to 4 carbon atoms or the benzyl or phenethyl radicals,
Z represents a functional group capable of reacting with a secondary amine functional group, xe2x95x90Nxe2x80x94H, to form an Nxe2x80x94C covalent bond,
with a compound of formula (Ixe2x80x2): 
in which:
Wxe2x80x21, Wxe2x80x22 and Wxe2x80x23, which are identical or different, each represent, independently of one another, a divalent radical chosen from those represented by the general formula (Axe2x80x2):
xe2x80x94[(CT1T2)nxe2x80x94[N(Rxe2x80x24)]pxe2x80x94(CT3T4)m]lxe2x80x94xe2x80x83xe2x80x83(Axe2x80x2)
xe2x80x83in which,
l, p, n, m, T1, T2, T3 and T4 have the same definition as for the formula (A) as defined above and
Rxe2x80x24 represents a hydrogen atom, a linear or branched alkyl radical comprising from 1 to 15 carbon atoms or a [(hetero)aryl]alkyl radical comprising from 7 to 12 carbon atoms,
Rxe2x80x21, Rxe2x80x22 and Rxe2x80x23, which are identical or different, each represent, independently of one another and of R4, a hydrogen atom, a linear or branched alkyl radical comprising from 1 to 15 carbon atoms or a [(hetero)aryl]alkyl radical comprising from 7 to 12 carbon atoms,
it being understood that the polyazacycloalkane nucleus of the compound of formula (I) comprises at most 30 cyclic carbon atoms and at most 6 cyclic nitrogen atoms and that at least one of these cyclic nitrogen atoms is
to form the compound of formula (I) as defined above and, if desired,
b) the functionalization of all or a portion of the unsubstituted cyclic nitrogens of said compound of formula (I) to form a compound of formula (Id), corresponding to the formula (I) as defined above in which at least one of the R1, R2, R3 or R4 radicals represents a radical xe2x80x94(CH2)wxe2x80x94C(xe2x95x90O)xe2x80x94V in which w and V are as defined above.
The term xe2x80x9cfunctional group capable of reacting with a secondary aminexe2x80x9d denotes in particular those which react according to a nucleophilic substitution mechanism, such as, for example, halogen radicals and in particular the bromo or iodo radicals, or those which react according to an electrophilic addition mechanism, such as, for example, the epoxy functional group, which results in an Nxe2x80x94CH2xe2x80x94CH(OH)xe2x80x94 fragment; it can also be a free, salified or esterified carboxyl functional group or an unsaturated group CH2xe2x95x90CHxe2x80x94, which results in an Nxe2x80x94CH2xe2x80x94CH2xe2x80x94 fragment by a reaction of xe2x80x9cMichaelxe2x80x9d type according to a nucleophilic addition mechanism.
These examples do not have a limiting nature and it is obvious that any functional group known to a person skilled in the art at the date of filing of the present patent application as being capable of reacting with a secondary amine functional group to form an Nxe2x80x94C covalent bond forms an integral part of the description of the present invention.
The compounds of formula (C1):
Zxe2x80x2xe2x80x94(CH2)oxe2x80x94(Q)qxe2x80x94(CH2)rxe2x80x94(Ar)sxe2x80x94(CH2)txe2x80x94(U)uxe2x80x94(CH2)vxe2x80x94Si(X)3(C1)
in which:
o, q, r, s, t, u, v, Q, Ar, U and X have the same definition as for the formula (B1) as defined above,
Zxe2x80x2 represents either a halo radical, in particular a bromo radical or an iodo radical, or an oxiran-2-yl group or an ethenyl group,
the sum q+s is equal to 0 or to 1, it being understood that, when q is equal to 1 and when Zxe2x80x2 represents a halo radical, o is other than 0,
that, when q is equal to 1 and when u is equal to 0, the sum r+s+t+v is other than 0,
that, when u is equal to 1, v is other than 0,
that, when u is equal to 1 and when q is equal to 0, the sum o+r+s+t is other than 0,
that, when s is equal to 0 and when q and u are each equal to 1, the sum r+t is other than 0, and
that the sum o+r+t+v is less than 6,
and in particular (triethoxy)(3-iodopropyl)silane, 2-[[[3-(triethoxysilyl)propyl]oxy]methyl]oxirane, N-[[4-(bromomethyl)phenyl]methyl]xe2x80x94N-[3-(triethoxysilyl)propyl]amine, (triethoxy)[4-(iodomethyl)phenyl]silane, 3-(triethoxysilyl)propyl propenoate or N-[3-(triethoxysilyl)propyl]bromoacetamide, are particularly appropriate in carrying out the process according to the invention.
According to another aspect of the present invention, a subject-matter of the latter is a polysiloxane gel (III) incorporating polyazamacrocycles and metal complexes of these nitrogenous ligands, which is capable of being obtained from the hydrolysis of the compound of formula (I) as defined above, resulting in the formation of a polysiloxane gel incorporating non-metallated polyazamacrocycle units (IIIxe2x80x2), followed by the action of a metal salt on said gel (IIIxe2x80x2), and the process for the preparation of the polysiloxane gel (IIIxe2x80x2) thus carried out starting from the compound of formula (I) as defined above.
According to another aspect of the present invention, a subject-matter of the latter is a polysiloxane gel (IV) incorporating polyazamacrocycles and metal complexes of these nitrogenous ligands, which is capable of being obtained from the action of a metal salt on the compound of formula (I) as defined above, resulting in the formation of an organometallic complex of said metal with said compound of formula (I), followed by the hydrolysis of said organometallic complex, and the process for the preparation of polysiloxane gel (IV) thus carried out starting from the compound of formula (I) as defined above.
The metal involved in the composition of the polysiloxane gel (III) or (IV) is chosen in particular from U, Pu, Am, Eu, Ce, Cr, Gd, Mn, Fe, Co, Ni, Cu, Zn, Ag, Cd, Au, Hg or Pb.
A more particular subject-matter of the present invention is hybrid materials (III4) and (IV1), corresponding respectively to the hybrid compounds (III) and (IV) in which the metal element is chosen from cobalt or copper, and more particularly materials (III1a) and (IV1a) capable of being obtained from the compound of formula (Ia), (Ib) or (Ic).
In a final aspect of the present invention, a subject-matter of the latter is the use of these metallated hybrid gels as defined above in separating a predetermined gas from a mixture of gases, wherein said mixture of gases is brought into contact with one of the metallated hybrid gels (III) or (IV) as defined above under conditions which make possible the absorption of said gas to be separated, followed by a phase of desorption of said gas attached to said gel and by a phase of recovery of said desorbed gas. This use is preferably applied to the separation of oxygen from the air, either for the purpose of producing pure oxygen or for the purpose of removing oxygen from the air.
The non-metallated gels (IIIxe2x80x2) can be employed in purifying liquids which absolutely have to be free from any metal cation, in particular those used in the electronics industry, such as, for example, dilute or concentrated hydrogen peroxide.
The non-metallated gels (IIIxe2x80x2) can also be employed in purifying gases by adsorption of the undesirable gaseous impurities
The following examples illustrate the invention and in particular the two routes described above for the synthesis, according to a sol-gel process, of novel polysiloxanes incorporating polyazacycloalkanes and metal complexes of these nitrogenous ligands.
As shown in these examples, the variety of the precursors used, the optional addition of tetraalkoxysilane during the gelling stage and the variations in the operating conditions make it possible to obtain materials with a variable composition and a variable texture, both in terms of concentration of ligand or of complex in the solid and of porosity and specific surface. Under strictly identical synthesis conditions, the solids obtained exhibit identical characteristics, thus showing good reproducibility of the method.
The advantages of this method thus lie essentially in the possibility of adjusting the characteristics of the material according to the requirements of materials engineering.